Photocatalytic Dinitrogen Reduction to Ammonia over Biomimetic FeMoSx Nanosheets

Reduction of atmospheric dinitrogen (N2) to ammonia (NH3) using water and sunlight in the absence of sacrificial reducing reagents at room temperature is very challenging and is considered an eco-friendly approach to meet the rapidly increasing demand for nitrogen storage, fertilizers, and a sustainable society. Currently, ammonia production via the energy-intensive Haber–Bosch process causes ∼350 million tons of carbon dioxide (CO2) emission per year. Interestingly, natural N2 fixation by the nitrogenase enzyme occurs under ambient conditions. Unfortunately, N2 fixation on biomimetic catalysts has rarely been studied. To mimic biological nitrogen fixation, herein, we synthesized the novel iron molybdenum sulfide (FeMoSx) micro-/nanosheets via a simple hydrothermal approach for the first time. Further, we successfully demonstrated the photochemical conversion of N2 to NH3 over a biomimetic FeMoSx photocatalyst. The estimated yield is around 99.79 ± 6.0 μmol/h/g photocatalyst with a quantum efficiency of ∼0.028% at 532 nm visible-light wavelength. Besides, we also systematically studied the influence of key factors to further improve NH3 yields. Overall, this study paves a new pathway to fabricate carbon-free, photochemical N2 fixation materials for future applications.


Figure S2 .Figure S3 .
Figure S2.High and low resolution HRTEM images of FMS catalyst.

Figure S8 .
Figure S8.Photograph of the reaction setup for photochemical dinitrogen reduction reaction.

Figure S17 .
Figure S17.TEM images of FMS catalyst: before and after photocatalytic reaction.

Figure S18 .
Figure S18.XPS analysis of FMS catalyst after photocatalytic reaction (A) in a wide range covering all Fe, O, Mo, S elements, (B) a magnified range between 735~700 eV for the Fe element, (C) a magnified range between 238~222 eV for various Mo oxidation states, and (D) 167~156 eV for the S element.

Figure S19 .
Figure S19.Possible mechanism of present photocatalytic N 2 fixation on FMS catalyst.

Table of contents S1. Supplementary figures Figure S1.
Figure S1.SEM images of FMS catalyst.-

Table S2 .
17 Comparing ammonia quantum yields over biomimetic photocatalysts reported in recent literature

Table S2 . Comparing ammonia quantum yields over biomimetic photocatalysts reported in recent literature.
Other factors that effectively influence the yield calculation such as light intensity, yield physical shape (i.e., solid, gas), weight of semiconductor and physical shape of the catalyst, are all crucial when comparing the yield in different catalyst.